1. Field of the Invention
This invention relates to the lighting arts, and in particular to an electronic auxiliary lighting system for a high intensity discharge lamp. More particularly, the auxiliary lighting system of the present invention uses as a light source a high output compact fluorescent lamp.
2. Description of Related Art
A high-intensity discharge (HID) lamp will extinguish when power to the HID lamp is interrupted. Momentary power interruptions, such as a lightning strike or someone inadvertently hitting the on/off switch, will cause the HID lamp to extinguish. An extinguished HID lamp will not immediately re-ignite upon the restoration of power to the HID lamp because gases within the HID lamp must be cooled before the HID lamp will re-ignite. With the power restored, restarting a hot HID lamp can take several minutes. Even when they are cool, and easy to start, HID lamps still take up to 2 minutes to come to full bright after they are ignited.
The garage building industry puts a great deal of stock in emergency lighting standards. The industry likes to see a certain minimum amount of light along path of egress in their structures during power interruptions. Accordingly, auxiliary lighting control circuitry has been used for automatically lighting an auxiliary light source, such as an incandescent lamp, following a brief power interruption of a HID lamp. It is known in the art to use quartz lamps to meet these emergency lighting requirements. Round and square garage lights having a HID lamp as a primary light source and a quartz auxiliary lamp have been used for many years. The premise is that when the HID lamp, located at the center of the fixture, is not on the quartz lamp, which is typically a smaller cylindrical incandescent lamp mounted to the side of the HID lamp, is lit to provide emergency illumination. However, there are inherent problems with these current practices of providing auxiliary light to garage lighting systems.
The quartz lamps that are typically used as auxiliary lamps are short lived and are very inefficient in converting electric power into lumens. This causes problems with continued reliability, maintenance, and the ability to meet auxiliary lighting needs. A significant problem associated with these current practices is that the quartz lamps are not located at the photometric center of the fixture. This causes the pattern of light projected from the auxiliary lamp to lack uniformity and thus portions of the lighted area are only dimly lit. Additionally, during normal operation the quartz lamp mounted on one side of the fixture blocks or refracts light from the HID lamp located at the center of the fixture. This causes the quartz lamp, during normal operation of the HID lamp, to form a shadow on the area being lit. It has also been found that emergency incandescent lamp sources are inherently glary and consistently mounted off of the centerline of the fixture, causing the luminaire to be aesthetically unappealing.
What is needed in the garage lighting industry is an auxiliary lamp system that provides emergency light without the problems found in the current systems.